My friend also has a FD and he is having a boost problem. We thought it was the crossover pipe but we replaced that and a couple other hoses with no avail. Here is the symptom. When he floors it in second gear he gets no more than 5 lbs of boost. If he just gently applies the gas it goes up to 10lbs. It also goes up to 10lbs in any other gear with no problem. I am at a complete loss. Anybody have any good ideas? And yes he plans on just replacing lines one bye one if neccessary but if someone has a better idea please let me know. Thanks

 

That's funny, one of my member's has that exact same problem!! I've NEVER heard of it or know of anyone else who had that same problem! I drove the car and was like...WTF??? Let me know if you find out what is wrong with yours.

 

Maybe it's a Southern thing...LOL.

 

there is only one thing I could see that might be causing the problem. Under the black plastic vacum tank there is a map sensor that has about 4 lines connected to it. One of them broke off. I told him to try replacing the sensor. But this has got to be the wierdest boost problem I have ever seen.

 

Mine does that sometimes as well.

 

You are talking about the one that has the two electrical connectors going to it, right??? It's more to the left when you are looking at the motor and bolts to the intake. If you are talking about this part, then this very well could be your problem and most likely is. I heard it has something to do with boost, but I am not exactly sure what it does. I did a hose job on my car and broke one of the nipples off of that switch/solenoid and had to replace it for 130.00 through mazda...

 

This happens no matter what? each and every time you can replicate this symptom?

 

yeah, it supposedly happens every time. I'm going to tell the guy I need to drive the car so I can see for myself exactly what the boost curve looks like. I don't think its the sensor only because it looks like the nipple doesn't allow any thing trough it (although that doesn't make much sense). Bye the way the forementioned sensor is the one I'm talking about.

 

I am trying to figure out what sensor you are talking about. Are you positive it is a sensor. The only sensor below the vacuum chamber is the crank angle position sensors.

Are you talking about the pressure chamber on top of the motor? And if so, where exactly is the four connector harness that you are talking about?

 

I almost forgto. When you do this test drive, make sure to detail as much as possible.

Things that we need to know.

What is the rolling speed when at WOT and yielding 5PSI?

What happens at 4500 RPM

What is the rolling speed when you start the gradual acceleration to 10psi?

What happens at 4500 RPM?

When in first, what happens?

When in 3rd, what happens?

If anybody can think of anything else to look for, let's give him it. I think that the more information we can get, the better we can help.